Answer / iamdon

The rotor is a structure having mass and elasticity.So it
will vibrate with a natural fcrequency which is balanced by
elastic force.The mass centre has an inherent eccentricity
from the centre of rotation.

The deflection tend to be very large near or at critical
speed and gives rise to considerable vibrations.This may
break the shaft.That is why rotating machines are not
allowed to run near or at critical speed.

Author:arbelectbit@yahoo.com

Answer / s.krishnan

critical speed is above 20 percentage of rated
speed.rotating machine rotate near to critical speed the
motor bearings are damaged.so rotating machines are not
allowed to run near critical speed region.

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